Electron Temperatures and Free-Electron Energy Distributions of Nebulae from C II Dielectronic Recombination Lines

Abstract

A recently generated theoretical line list of C II dielectronic recombination lines together with observational data gathered from the literature is used to investigate the electron temperature in a range of astronomical objects, mainly planetary nebulae. The electron temperature is obtained by a least-squares optimisation using all the reliable observed lines in each object. In addition, the subset of lines arising directly from autoionising states is used to directly determine the free-electron energy distribution which is then compared with various theoretical possibilities. The method described here can potentially determine whether there are departures from Maxwell-Boltzmann distributions in some nebulae, as has been recently proposed. Using published observations of the three planetary nebulae where the relevant lines are recorded, we find that the data are best matched by Maxwell-Boltzmann distributions but that the uncertainties are sufficiently large at present that kappa-distributions or two-component nebular models are not excluded.

arXiv comment13 pages, 13 figures, 3 tables

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Cited by in corpus (19)

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• The Continuum Emission Spectrum of Hf 2-2 near the Balmer Limit and the ORL versus CEL abundance and temperature Discrepancy
• Very Large Telescope deep echelle spectroscopy of Galactic planetary nebulae NGC 6153, M 1-42 and Hf 2-2
• Emission and recombination coefficients for hydrogen with kappa-distributed electron energies
• Atomic Data Assessment with PyNeb: Radiative and Electron Impact Excitation Rates for [Fe II] and [Fe III]
• Effective collision strengths for excitation and de-excitation of nebular [O III] optical and infrared lines with kappa distributed electron energies
• On the non-thermal kappa-distributed electrons in planetary nebulae and HII regions: the kappa index and its correlations with other nebular properties
• Critically Evaluated Spectral Data for Singly Ionized Carbon (C II)
• First evidence of enhanced recombination in astrophysical environments and the implications for plasma diagnostics
• Discovery of a Rare Late-Type, Low-Mass Wolf-Rayet Star in the LMC
• Physical and chemical properties of Wolf-Rayet planetary nebulae
• The ultraviolet CII lines as a diagnostic of kappa-distributed electrons in planetary nebulae
• Electron Energy Distributions in the Extended Gas Nebulae associated with High-z AGN: Maxwell-Boltzmann vs. kappa distributions
• Methods for Analyzing Resonances in Atomic Scattering
• Can the Kappa-distributed electron energies account for the intensity ratios of O II lines in photoionized gaseous nebulae?
• Physical Conditions and Chemical Abundances of the Variable Planetary Nebula IC 4997
• Multi-diagnostic convergence: a single measurement in weakly collisional plasmas